1. Field of the Invention
The present invention relates to a scheme for displaying an electronic map, and more particularly, to an electronic map display system and related method for using a plurality of attributes corresponding to a plurality of target objects to control a display order regarding the target objects for displaying the target objects.
2. Description of the Prior Art
Generally speaking, if a person is at an unfamiliar location in a particular geographic environment, he/she can use an electronic map display system to find an important landmark nearby. This person must find his/her relative position (corresponding to his/her current unfamiliar location) on an electronic map to determine the general direction in which to proceed in order to arrive at the next location. At present, when using a conventional electronic map display system (e.g. a vehicle navigation system) to display a smaller section of the electronic map (e.g. corresponding to the unfamiliar location in the particular geographic environment mentioned above), a user can find his/her location relative to the particular geographic environment in two different ways. One way is to directly use a scrollbar on the display system to change a display range currently displayed on the screen. Although the idea of this method is simple and direct, the electronic map display system displays all target objects (corresponding to landmarks and included by an electronic map manufacturing company) within the display range each time the display range is changed. This will cause a delay in the display screen while all the target objects in the display range are redrawn each time the scrollbar is moved. Therefore, although using the scrollbar to change the display range for finding out the position is very simple, much time is wasted waiting for the new display range and target objects to be redrawn. Additionally, the other way to find his/her location relative to the particular geographic environment is to change a scale on the electronic map. That is, the user can change the scale to narrow the display range currently shown on the screen and to enlarge a range on the electronic map (i.e. zoom in for a “closer” view). Accordingly, the changed display range will comprise an enlarged display range on the electronic map on the display screen. However, since the scale is enlarged, the electronic map display system may selectively not display target object(s) having over-detailed information when displaying objects within the changed display range. For example, before enlarging the scale on the electronic map, the electronic map display system displays all target objects (e.g. it displays both an important road and a branch road on the display screen). After enlarging the scale, the electronic map display system may only display the important road without displaying the branch road on the display screen so that information viewed by the user is not overcrowded and a computing time delay required by the electronic map display system (for displaying object(s)) can be decreased. However, this makes it inconvenient for the user in finding his/her position on the electronic map, because unlike the experience of viewing a real map, the user must change the scale many times and can never immediately browse other positions on the electronic map but that are out of the display range. In summary, using such a conventional electronic map display system is inconvenient and requires multiple user actions to achieve a single task.